Video is part of a full report on what the bureau knows about Aaron Alexis so far.

Video footage just released by the FBI shows 34-year-old Aaron Alexis as he entered the D.C. Navy Yard before the shooting began. The video is part of this full report released by the FBI, that includes everything the agency knows about Alexis so far. The report has detailed pictures of the rifle Alexis used during the shooting, including close ups of the many strange engravings on the bottom and sides of the gun.

The video pinpoints the car Alexis used to enter the facility's parking garage where, much later, many of the buildings employees would hide while law enforcement tried to contain the situation. Alexis can be seen setting up his rifle and then sneaking between floors before opening fire on the unsuspecting Navy Yard employees.

The report also confirms much of the information we already know. In the days leading up to the shooting, Alexis bought the Remington shotgun from a gun store in Virginia. He was employed as a contractor and was stationed at the Navy Yard beginning at the end of August. Because of his past work in the Navy and his current employment with a contractor, Alexis had full access to the Navy Yard. Then, on September 16, Alexis entered the D.C. Navy Yard building and killed 12 people and injured four more.